1. Field of the Invention
This invention relates to an extracting apparatus for extracting a predetermined substance such as a nucleic acid from a sample liquid by use of at least one extracting cartridge provided with a filter member. This invention particularly relates to extraction of the predetermined substance through pressurization of an area within at least one extracting cartridge with pressurized air introduced into the extracting cartridge.
2. Description of the Related Art
As extracting methods, for example in techniques for extracting a nucleic acid, a centrifugal technique, a technique utilizing magnetic beads, a technique utilizing a filter, and the like, have heretofore been known.
For example, there has been proposed a nucleic acid extracting apparatus utilizing filters. With the proposed nucleic acid extracting apparatus, a plurality of filter tubes, each of which accommodates a filter therein, are set on a rack, and sample liquids are respectively injected into the filter tubes. Also, a region around a bottom of the rack is closed with an air chamber via a sealing material, and a pressure within the air chamber is reduced. Areas within all of the filter tubes are thus simultaneously subjected to suction from discharging sides of the filter tubes, and the sample liquids contained in the filter tubes are thus caused to pass through the filters of the filter tubes. Nucleic acids contained in the sample liquids are thus adsorbed to the filters of the filter tubes. Thereafter, a washing liquid and an eluting liquid are successively injected into the filter tubes and subjected to suction at a reduced pressure. The nucleic acids having been adsorbed to the filters of the filter tubes are thus washed with the washing liquid and eluted from the filters. (The aforesaid nucleic acid extracting apparatus utilizing filters is described in, for example, U.S. Pat. No. 5,645,723.)
As described above, a separation purification method of a nucleic acid, comprising the step of using a predetermined filter for separating and recovering the sample liquid after the nucleic acid contained in the sample liquid is adsorbed to the filter, is disclosed in U.S. Patent Laid-Open No. 20030170664. Further, a method for extracting by injecting the sample liquid into the separation purification unit including the filter and pressurizing the sample liquid is adopted.
However, the conventional nucleic acid extracting apparatus described above has the problems in that, in cases where the nucleic acid extracting apparatus has a large size so as to be appropriate for analyses of large amounts of samples and in cases where the number of the samples is small, and the frequency of analyses is low, the cost of the nucleic acid extracting apparatus is not capable of being kept low, and the processing efficiency is not capable of being kept high.
Also, as for nucleic acid extracting apparatuses, it is desired that the processing is capable of being performed quickly and efficiently without any contamination occurring, and that the sizes of the nucleic acid extracting apparatuses are capable of being kept small. However, the problems described below occur with the nucleic acid extracting apparatus proposed in U.S. Pat. No. 5,645,723.
Specifically, with a nucleic acid extracting apparatus, in which the areas within all of the filter tubes are simultaneously subjected to suction as in the cases of the nucleic acid extracting apparatus proposed in U.S. Pat. No. 5,645,723, in cases where the sample liquids have different characteristics as in the cases of sampled whole blood, at the time at which the suction with respect to a certain filter tube is completed, and the resistance against the suction with respect to the certain filter tube disappears, the effect of the reduced pressure acting upon the other filter tubes becomes small. As a result, the problems often occur in that the processing on sample liquids having a comparatively high viscosity is not capable of being completed. In cases where the capacity of the reduced pressure is increased in order to prevent the aforesaid problems from occurring, the size of the extracting apparatus is not capable of being kept small. Also, due to a large volume of the reduced pressure, a long time is required to obtain the reduced pressure. Further, it is not always possible to detect the completion of the discharging of all of the sample liquids. Therefore, the setting time is not capable of being kept short, and the processing efficiency is not capable of being enhanced. Furthermore, the problems occur in that a sample liquid having a low viscosity is vigorously discharged from the filter tube, and a bubble-like splash of the sample liquid clings to an adjacent filter tube and an adjacent area of the rack and causes contamination to occur. As a result, the accuracy of the analysis is not capable of being kept high.
In particular, with the extracting apparatus, in which the areas within all of the filter tubes are simultaneously subjected to vacuum suction, the problems occur in that, in cases where air resistance does not occur in one of the filter tubes due to a sample liquid injection failure, a filter tube loading failure, or the like, a normal operation is not capable of being performed. Also, it is not always possible to constitute a mechanism for performing independent sucking operation for each of the plurality of the filter tubes.
A method for recovering the liquid by adsorbing the nucleic acid to the filter by pressurization is disclosed in U.S. Patent Laid-Open No. 20030170664. However, a specific extracting apparatus is not disclosed. In the extracting apparatus which adopts the pressurization method, problems will arise in its pressurization control method. Problems will also arise in contamination due to scattering of the discharged liquid during pressurization, reliability in sealing, or the like.